<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>z-index</title>
	<style>
	div {
		width:200px;
		height: 200px;
	}
	.div1 {
		position: absolute;
		left:50px;
		top:50px;
		background: red;
		z-index:1;
	}
	.div2 {
		position: absolute;
		left:100px;
		top:100px;
		background: green;
		z-index:2;
	}
	.div3 {
		position: absolute;
		left:150px;
		top:150px;
		background: blue;
		z-index:3;
	}
	</style>
</head>
<body>
	<div class="div1"></div>
	<div class="div2"></div>
	<div class="div3"></div>
</body>
</html>